The jump in sales of newly-built homes is of particular note, as housing construction has typically played a lead role in past US economic recoveries.

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Most of the high-rise office buildings built in those cities before the mid-1990s do not meet current standards for new construction, and most of them have not been upgraded, said Hamburger.

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The 13 billion gallons or so of grain-based capacity already built or under construction was grandfathered in.

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They built affordable housing in the 1980s, then switched to high-end condo construction.

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Banks have learned some hard lessons and are seeking to hedge their bets on construction loans that are viewed as higher risk, in part because half-built properties can be hard to sell if the projects stall.

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